Move automatic text track selection code to AutomaticTrackSelection helper

Source/core/html/track/AutomaticTrackSelection.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef AutomaticTrackSelection_h
+#define AutomaticTrackSelection_h
+
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class TextTrackList;
+class TrackGroup;
+
+class AutomaticTrackSelection {
+    STACK_ALLOCATED();
+public:
+    struct Configuration {
+        Configuration()
+            : disableCurrentlyEnabledTracks(false)
+            , forceEnableSubtitleOrCaptionTrack(false) { }
+
+        bool disableCurrentlyEnabledTracks;
+        bool forceEnableSubtitleOrCaptionTrack;
+    };
+
+    AutomaticTrackSelection(TextTrackList*, const Configuration&);
+
+    void perform();
+
+private:
+    void performAutomaticTextTrackSelection(const TrackGroup&);
+    void enableDefaultMetadataTextTracks(const TrackGroup&);
+
+    RawPtrWillBeMember<TextTrackList> m_textTracks;

[philipj_slow, 2015/02/11 03:00:24]

Could we make this an argument to perform() to save readers the trouble of even
thinking about life time?

[fs, 2015/02/11 10:02:26]

Done. (Wanted to make it 'const' too, but apparently item() isn't const... I'll
look at that and maybe fix in a separate CL.)

[philipj_slow, 2015/02/11 10:29:54]

Well, it does modify the members of the list, so even if const could be made to
work it may give the wrong impression.

+    Configuration m_configuration;

[philipj_slow, 2015/02/11 03:00:24]

Make it const to document that performing track selection doesn't change the
configuration, and thus that a AutomaticTrackSelection object *could* be used
multiple times? (That would only happen in unit tests, though.)

[fs, 2015/02/11 10:02:26]

Done. (Unit-testability would require passing the language list too, but that
should be doable.)

+};
+
+} // namespace blink
+
+#endif // AutomaticTrackSelection_h